scholarly journals Balancing cholesterol in the brain: from synthesis to disposal

2022 ◽  
pp. 1-27
Author(s):  
Lydia Qian ◽  
Amanda B. Chai ◽  
Ingrid C. Gelissen ◽  
Andrew J. Brown
Keyword(s):  
De Novo ◽  
Cholesterol Metabolism ◽  
Peripheral Circulation ◽  
The Body ◽  
Cholesterol Homeostasis ◽  
Myelin Sheaths ◽  
The Central Nervous System ◽  
Vital Component ◽  
The Brain ◽  
Limited Exchange

The cholesterol is a vital component of cell membranes and myelin sheaths, and a precursor for essential molecules such as steroid hormones. In humans, cholesterol is partially obtained through the diet, while the majority is synthesized in the body, primarily in the liver. However, the limited exchange between the central nervous system and peripheral circulation, due to the presence of the blood-brain barrier, necessitates cholesterol in the brain to be exclusively acquired from local de novo synthesis. This cholesterol is reutilized efficiently, rendering a much slower overall turnover of the compound in the brain as compared with the periphery. Furthermore, brain cholesterol is regulated independently from peripheral cholesterol. Numerous enzymes, proteins, and other factors are involved in cholesterol synthesis and metabolism in the brain. Understanding the unique mechanisms and pathways involved in the maintenance of cholesterol homeostasis in the brain is critical, considering perturbations to these processes are implicated in numerous neurodegenerative diseases. This review focuses on the developing understanding of cholesterol metabolism in the brain, discussing the sites and processes involved in its synthesis and regulation, as well as the mechanisms involved in its distribution throughout, and elimination from, the brain.

scholarly journals Kynurenine Pathway Metabolism is Involved in the Maintenance of the Intracellular NAD+ Concentration in Human Primary Astrocytes

2010 ◽  
Vol 3 ◽  
pp. IJTR.S4779 ◽  
Author(s):  
Ross Grant ◽  
Susan Nguyen ◽  
Gilles Guillemin
Keyword(s):  
Nicotinic Acid ◽  
De Novo ◽  
Culture Media ◽  
Kynurenine Pathway ◽  
The Body ◽  
Tryptophan Degradation ◽  
Major Cell Type ◽  
The Central Nervous System ◽  
The Relationship ◽  
The Brain

Efficient synthesis of NAD+ is critical to maintaining cell viability in all organs of the body. However, little is known of the pathway(s) by which cells of the central nervous system produce NAD+. The aim of this study was to investigate the relationship, between tryptophan degradation via the kynurenine pathway (KP) and de novo NAD+ synthesis in human astrocytes, a major cell type within the brain. In this study we observed that inhibition of single enzymes of the KP resulted in significant decreases in NAD+ levels in astroglial cells after a 24 hr period. We also observed that astrocytes cultured in media deficient in tryptophan, nicotinic acid and nicotinamide resulted in a 50% decrease in NAD+ levels after 24 hrs. This decrease in NAD+ was partially restored by supplementation of the culture media with either tryptophan or kynurenine, or nicotinic acid or with supply of the salvage pathway precursor nicotinamide.

scholarly journals Cholesterol Metabolism: A Potential Therapeutic Target in Glioblastoma

Cancers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 146 ◽  
Author(s):  
Fahim Ahmad ◽  
Qian Sun ◽  
Deven Patel ◽  
Jayne Stommel
Keyword(s):  
Brain Tumors ◽  
Cholesterol Synthesis ◽  
De Novo ◽  
Cholesterol Metabolism ◽  
Dietary Cholesterol ◽  
The Body ◽  
Adult Brain ◽  
Normal Brain ◽  
New Strategy ◽  
The Brain

Glioblastoma is a highly lethal adult brain tumor with no effective treatments. In this review, we discuss the potential to target cholesterol metabolism as a new strategy for treating glioblastomas. Twenty percent of cholesterol in the body is in the brain, yet the brain is unique among organs in that it has no access to dietary cholesterol and must synthesize it de novo. This suggests that therapies targeting cholesterol synthesis in brain tumors might render their effects without compromising cell viability in other organs. We will describe cholesterol synthesis and homeostatic feedback pathways in normal brain and brain tumors, as well as various strategies for targeting these pathways for therapeutic intervention.

scholarly journals Impact of Cholesterol Metabolism in Immune Cell Function and Atherosclerosis

Nutrients ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2021 ◽  
Author(s):  
María Aguilar-Ballester ◽  
Andrea Herrero-Cervera ◽  
Ángela Vinué ◽  
Sergio Martínez-Hervás ◽  
Herminia González-Navarro
Keyword(s):  
Immune Cells ◽  
Immune Cell ◽  
De Novo ◽  
Cholesterol Metabolism ◽  
The Body ◽  
Cholesterol Homeostasis ◽  
Hematopoietic Stem ◽  
Regulatory Pathways ◽  
Cholesterol Levels ◽  
Atherosclerosis Development

Cholesterol, the most important sterol in mammals, helps maintain plasma membrane fluidity and is a precursor of bile acids, oxysterols, and steroid hormones. Cholesterol in the body is obtained from the diet or can be de novo synthetized. Cholesterol homeostasis is mainly regulated by the liver, where cholesterol is packed in lipoproteins for transport through a tightly regulated process. Changes in circulating lipoprotein cholesterol levels lead to atherosclerosis development, which is initiated by an accumulation of modified lipoproteins in the subendothelial space; this induces significant changes in immune cell differentiation and function. Beyond lesions, cholesterol levels also play important roles in immune cells such as monocyte priming, neutrophil activation, hematopoietic stem cell mobilization, and enhanced T cell production. In addition, changes in cholesterol intracellular metabolic enzymes or transporters in immune cells affect their signaling and phenotype differentiation, which can impact on atherosclerosis development. In this review, we describe the main regulatory pathways and mechanisms of cholesterol metabolism and how these affect immune cell generation, proliferation, activation, and signaling in the context of atherosclerosis.

The Impact of Phytosterols on the Healthy and Diseased Brain

2019 ◽  
Vol 26 (37) ◽  
pp. 6750-6765 ◽  
Author(s):  
Tess Dierckx ◽  
Jeroen F.J. Bogie ◽  
Jerome J.A. Hendriks
Keyword(s):  
Cholesterol Metabolism ◽  
Neurological Diseases ◽  
Physiological Role ◽  
Cholesterol Homeostasis ◽  
Brain Functioning ◽  
The Central Nervous System ◽  
And Function ◽  
The Impact ◽  
The Brain

The central nervous system (CNS) is the most cholesterol-rich organ in mammals. Cholesterol homeostasis is essential for proper brain functioning and dysregulation of cholesterol metabolism can lead to neurological problems. Multiple sclerosis (MS) and Alzheimer’s disease (AD) are examples of neurological diseases that are characterized by a disturbed cholesterol metabolism. Phytosterols (PS) are plant-derived components that structurally and functionally resemble cholesterol. PS are known for their cholesterol-lowering properties. Due to their ability to reach the brain, researchers have started to investigate the physiological role of PS in the CNS. In this review, the metabolism and function of PS in the diseased and healthy CNS are discussed.

scholarly journals Limbic Expression of mRNA Coding for Chemoreceptors in Human Brain—Lessons from Brain Atlases

2021 ◽  
Vol 22 (13) ◽  
pp. 6858
Author(s):  
Fanny Gaudel ◽  
Gaëlle Guiraudie-Capraz ◽  
François Féron
Keyword(s):  
G Proteins ◽  
The Body ◽  
Trace Amines ◽  
Chemical Senses ◽  
Brain Areas ◽  
Genes Encoding ◽  
The Central Nervous System ◽  
Human Brains ◽  
The Brain ◽  
Brain Atlases

Animals strongly rely on chemical senses to uncover the outside world and adjust their behaviour. Chemical signals are perceived by facial sensitive chemosensors that can be clustered into three families, namely the gustatory (TASR), olfactory (OR, TAAR) and pheromonal (VNR, FPR) receptors. Over recent decades, chemoreceptors were identified in non-facial parts of the body, including the brain. In order to map chemoreceptors within the encephalon, we performed a study based on four brain atlases. The transcript expression of selected members of the three chemoreceptor families and their canonical partners was analysed in major areas of healthy and demented human brains. Genes encoding all studied chemoreceptors are transcribed in the central nervous system, particularly in the limbic system. RNA of their canonical transduction partners (G proteins, ion channels) are also observed in all studied brain areas, reinforcing the suggestion that cerebral chemoreceptors are functional. In addition, we noticed that: (i) bitterness-associated receptors display an enriched expression, (ii) the brain is equipped to sense trace amines and pheromonal cues and (iii) chemoreceptor RNA expression varies with age, but not dementia or brain trauma. Extensive studies are now required to further understand how the brain makes sense of endogenous chemicals.

Cholecystokinin octapeptide analogues suppress food intake via central CCK-A receptors in mice

1993 ◽  
Vol 265 (3) ◽  
pp. R481-R486 ◽  
Author(s):  
Y. Hirosue ◽  
A. Inui ◽  
A. Teranishi ◽  
M. Miura ◽  
M. Nakajima ◽  
...  
Keyword(s):  
Food Intake ◽  
Receptor Antagonist ◽  
Rank Order ◽  
Peripheral Circulation ◽  
Inhibitory Effect ◽  
Peripheral Tissues ◽  
Cholecystokinin Octapeptide ◽  
The Central Nervous System ◽  
The Difference ◽  
The Brain

To examine the mechanism of the satiety-producing effect of cholecystokinin (CCK) in the central nervous system, we compared the potency of intraperitoneally (ip) or intracerebroventricularly (icv) administered CCK-8 and its analogues on food intake in fasted mice. The icv administration of a small dose of CCK-8 (0.03 nmol/brain) or of Suc-(Thr28, Leu29, MePhe33)-CCK-7 (0.001 nmol/brain) suppressed food intake for 20 min, whereas CCK-8 (1 nmol/kg, which is equivalent to 0.03 nmol/brain) or Suc-(Thr28, Leu29, MePhe33)-CCK-7 (1 nmol/kg) had satiety effect after ip administration. Dose-response studies indicated the following rank order of potency: Suc-CCK-7 > or = Suc-(Thr28, Leu29, MePhe33)-CCK-7 > or = CCK-8 > or = (Nle28,31)-CCK-8 >> desulfated CCK-8 = CCK-4 = 0 in the case of ip administration and Suc-(Thr28, Leu29, MePhe33)-CCK-7 >> Suc-CCK-7 > or = CCK-8 > or = (Nle28,31)-CCK-8 >> desulfated CCK-8 = CCK-4 = 0 in the case of icv administration. The selective CCK-A receptor antagonist MK-329 reversed the inhibitory effect of the centrally as well as peripherally administered CCK-8, or of Suc-(Thr28, Leu29, MePhe33)-CCK-7, whereas the selective CCK-B receptor antagonist L-365260 did not. The icv administered CCK-8 did not appear in the peripheral circulation. These findings suggest the participation of CCK-A receptors in the brain in mediating the satiety effect of CCK and the difference in CCK-A receptors in the brain and peripheral tissues.

Genetic defects in sterol synthesis, absorption, and degradation into bile acids

2011 ◽  
pp. 1673-1676
Author(s):  
Stefano Romeo
Keyword(s):  
Membrane Permeability ◽  
Bile Acids ◽  
Steroid Hormones ◽  
Cell Membranes ◽  
De Novo ◽  
Cholesterol Metabolism ◽  
The Body ◽  
Sterol Synthesis ◽  
Genetic Defects ◽  
And Function

Cholesterol is the most abundant steroid in animals. Not only is it a vital constituent of cell membranes, where it establishes proper membrane permeability and fluidity, but it is also the immediate metabolic precursor of all known steroid hormones and bile acids. Synthesized de novo in cells or absorbed from the diet, cholesterol circulates in the body in association with lipoproteins and is ultimately degraded into bile acids by the liver. Every perturbation of the numerous enzymes involved in cholesterol metabolism leads to impairment in the development and function of the gastrointestinal, cardiovascular, skeletal, and nervous systems.

scholarly journals Immune cells and CNS physiology: Microglia and beyond

2018 ◽  
Vol 216 (1) ◽  
pp. 60-70 ◽  
Author(s):  
Geoffrey T. Norris ◽  
Jonathan Kipnis
Keyword(s):  
Central Nervous System ◽  
Immune Cells ◽  
Brain Function ◽  
Brain Parenchyma ◽  
The Body ◽  
Immune Repertoire ◽  
Perivascular Macrophages ◽  
The Central Nervous System ◽  
Cns Immunity ◽  
The Brain

Recent advances have directed our knowledge of the immune system from a narrative of “self” versus “nonself” to one in which immune function is critical for homeostasis of organs throughout the body. This is also the case with respect to the central nervous system (CNS). CNS immunity exists in a segregated state, with a marked partition occurring between the brain parenchyma and meningeal spaces. While the brain parenchyma is patrolled by perivascular macrophages and microglia, the meningeal spaces are supplied with a diverse immune repertoire. In this review, we posit that such partition allows for neuro–immune crosstalk to be properly tuned. Convention may imply that meningeal immunity is an ominous threat to brain function; however, recent studies have shown that its presence may instead be a steady hand directing the CNS to optimal performance.

scholarly journals Monosodium Glutamate in the Diet Does Not Raise Brain Glutamate Concentrations or Disrupt Brain Functions

2018 ◽  
Vol 73 (Suppl. 5) ◽  
pp. 43-52 ◽  
Author(s):  
John D. Fernstrom
Keyword(s):  
Monosodium Glutamate ◽  
Safety Evaluation ◽  
The Body ◽  
Neuronal Function ◽  
Excitatory Neurotransmitter ◽  
Brain Functions ◽  
The Central Nervous System ◽  
Experimental Findings ◽  
The Brain ◽  
Amino Acid Glutamate

The non-essential amino acid glutamate participates in numerous metabolic pathways in the body. It also performs important physiologic functions, which include a sensory role as one of the basic tastes (as monosodium glutamate [MSG]), and a role in neuronal function as the dominant excitatory neurotransmitter in the central nervous system. Its pleasant taste (as MSG) has led to its inclusion as a flavoring agent in foods for centuries. Glutamate’s neurotransmitter role was discovered only in the last 60 years. Its inclusion in foods has necessitated its safety evaluation, which has raised concerns about its transfer into the blood ultimately increasing brain glutamate levels, thereby causing functional disruptions because it is a neurotransmitter. This concern, originally raised almost 50 years ago, has led to an extensive series of scientific studies to examine this issue, conducted primarily in rodents, non-human primates, and humans. The key findings have been that (a) the ingestion of MSG in the diet does not produce appreciable increases in glutamate concentrations in blood, except when given experimentally in amounts vastly in excess of normal intake levels; and (b) the blood-brain barrier effectively restricts the passage of glutamate from the blood into the brain, such that brain glutamate levels only rise when blood glutamate concentrations are raised experimentally via non-physiologic means. These and related discoveries explain why the ingestion of MSG in the diet does not lead to an increase in brain glutamate concentrations, and thus does not produce functional disruptions in brain. This article briefly summarizes key experimental findings that evaluate whether MSG in the diet poses a threat to brain function.

scholarly journals 27-Hydroxycholesterol Promotes the Transfer of Astrocyte-Derived Cholesterol to Neurons in Co-cultured SH-SY5Y Cells and C6 Cells

2020 ◽  
Vol 8 ◽  
Author(s):  
Yushan Wang ◽  
Xiaona Zhang ◽  
Tao Wang ◽  
Wen Liu ◽  
Lijing Wang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cholesterol Metabolism ◽  
Feedback Mechanism ◽  
Cholesterol Homeostasis ◽  
Membrane Cholesterol ◽  
C6 Cells ◽  
Cholesterol Accumulation ◽  
Cholesterol Levels ◽  
Related Proteins ◽  
The Brain

Abnormality in cholesterol homeostasis in the brain is a feature of Alzheimer’s disease (AD). 27-Hydroxycholesterol (27-OHC) has been identified as a possible biomarker of AD, but its effects on cholesterol metabolism have not been fully characterized. This study was aimed to investigate the impacts of 27-OHC on cholesterol metabolism in nerve cells. SH-SY5Y cells and C6 cells were co-cultured and treated with 5, 10, and 20 μM 27-OHC for 24 h. Results showed that 27-OHC decreased cholesterol levels and up-regulated the expression of transport-related proteins in C6 cells. In SH-SY5Y cells, 27-OHC increased cholesterol accumulation, especially on plasma membrane (PM), which was consistent with the up-regulation of expressions of cholesterol endocytosis receptors, lipid raft-related proteins, and cholesterol esterase. Simultaneously, accumulation of membrane cholesterol promoted cholesterol conversion to 24S-OHC by CYP46A1(24S-hydroxylase) transfer from the endoplasmic reticulum (ER) to PM. Besides, Aβ levels were elevated in SH-SY5Y cells after 27-OHC treatment. Our results suggest that 27-OHC motivates the transfer of astrocyte-derived cholesterol to neurons. Although there exists a feedback mechanism that excessive cholesterol promotes its conversion to 24S-OHC, the increased cholesterol induced by 27-OHC could not be wholly offset in neurons.

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